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In a recirculation aquaculture system the drumfilter effluent can be used as substrate for heterotrophic bacterial production, which can be recycled as feed. Because the bacteria might contain pathogens, which could reduce its sui...
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In a recirculation aquaculture system the drumfilter effluent can be used as substrate for heterotrophic bacterial production, which can be recycled as feed. Because the bacteria might contain pathogens, which could reduce its suitability as feed, it is important to characterize these communities. Bacteria were produced in growth reactors under different conditions: 7 h hydraulic retention time (HRT) vs. 2 h, sodium acetate vs. molasses, and ammonia vs. nitrate. The community of the drumfilter effluent was different from those found in the reactors. However, all major community components were present in the effluent and reactor broths. HRT influenced the bacteria community, resulting in a DGGE profile dominated by a band corresponding to an Acinetobacter sp.-related population at 2 h HRT compared to 7 h HRT, where bands indicative of alpha-proteobacterial populations most closely related to Rhizobium and Shinella spp. were most abundant. Molasses influenced the bacterial community. It was dominated by an Aquaspirillum serpens-related population. Providing total ammonia nitrogen (TAN) in addition to nitrate led to the occurrence of bacteria close to Sphaerotilus spp., Flavobacterium mizutaii and Jonesia spp. It was concluded from these results that a 6-7 h HRT is recommended, and that the type of substrate is less important, and results in communities with a comparably low pathogenic risk.
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During the workshop, the short lectures of several research groups were presented. The report covers both the presentations and subsequent discussion session.
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Anguillid herpesvirus (AnHV, also known as Herpesvirus anguillae or HVA) is found in both Japanese and European eels. Based on restriction enzyme analysis a small number of differences were found between AnHV isolated from Japanes...
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Anguillid herpesvirus (AnHV, also known as Herpesvirus anguillae or HVA) is found in both Japanese and European eels. Based on restriction enzyme analysis a small number of differences were found between AnHV isolated from Japanese eels and from European eels. The total genome size of both is about 245 kb, which is confirmed by alternating-field electrophoresis. Using a set of degenerate primers based on conserved regions within DNA-directed DNA polymerase coding regions, a 463 base pair fragment was isolated from both Japanese and European AnHV. Nucleotide sequence analysis showed that the cloned regions of both viruses have identical sequences. Based on this part of the DNA-polymerase sequence, primers were selected and used to develop a sensitive PCR to detect AnHV DNA in eel tissue samples. To avoid false negative results and to estimate the number of AnHV genome copies found in tissues, 100 copies of an internal control plasmid were added to the tissue samples. This semi-quantitative AnHV PCR can be used for both the European and Japanese isolates of AnHV, detects as few as 10 genome copies and is 100 times more sensitive than standard virus isolation.
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We show that European eels infected with the rhabdovirus EVEX (Eel Virus European X) virus, developed hemorrhage and anemia during simulated migration in large swim tunnels, and died after 1000-1500 km. In contrast, virus-negative...
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We show that European eels infected with the rhabdovirus EVEX (Eel Virus European X) virus, developed hemorrhage and anemia during simulated migration in large swim tunnels, and died after 1000-1500 km. In contrast, virus-negative animals swam 5500 km, the estimated distance to the spawning ground of the European eel in the Sargasso Sea. Virus-positive eels showed a decline in hematocrit, which was related to the swim distance. Virus-negative eels showed a slightly, increased hematocrit. Observed changes in plasma lactate dehydrogenase (LDH), total protein and aspartate aminotransferase (AAT) are indicative of a serious viral infection. Based on these observations, we conclude that eel virus infections may adversely affect the spawning migration of eels, and could be a contributing factor to the worldwide decline of eel. (c) 2005 Elsevier Inc. All rights reserved.
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EVEX (Eel-Virus-European-X), HVA (Herpesvirus anguillae), and EVE (Eel Virus European) were detected in wild and farmed European eels (Anguilla anguilla L.) from the Netherlands, EVEX and EVE from farmed eels from Italy, and EVEX ...
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EVEX (Eel-Virus-European-X), HVA (Herpesvirus anguillae), and EVE (Eel Virus European) were detected in wild and farmed European eels (Anguilla anguilla L.) from the Netherlands, EVEX and EVE from farmed eels from Italy, and EVEX from wild eels from Morocco. EVEX was also isolated from wild New Zealand eel (A. dieffenbachi). Elvers (A. anguilla) collected from eel farms in the Netherlands were mainly infected with HVA. An unknown picornavirus was isolated from healthy wild European eel from The Netherlands, and New Zealand eel (A. dieffenbachi) from New Zealand. European eels from Northern Ireland showed clinical signs of virus infections although no viruses were detected in these samples.
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